Can You Exercise When You're Sick?

Just yesterday, cold weather forced me to put on a coat for the first time in a while, and as temperatures begin to dip, cold and flu season will set in. As a matter of fact, listener Eric recently asked:

“I've just come down with an obnoxious sore throat, accompanied with a lot of aches and chills. One thing I'm wondering is how should I exercise when I am sick? I obviously don't want to go jogging in the cold, exacerbate symptoms, and make it harder to recover. But lying in bed, eating a lot, and getting fat is probably not the best approach either. I know that advice on this question would definitely depend on the severity of the illness, but are there some general guidelines?”

In this article, you’ll find out if you can exercise when you’re sick and what kind of workouts to do if you have a cold or flu.

Exercise Strengthens the Immune System

It’s a fact – regular physical activity strengthens your immune system. Studies have shown that recreational exercisers report fewer colds when they run regularly, and moderate exercise has been associated with a stronger immune system response and an increase in the production of macrophages, the cells that attack bacteria.

When you exercise, you improve blood flow and movement of your immune system’s lymphatic fluid, so your immune cells can circulate through the body more quickly to kill bacteria and viruses more efficiently.

The more consistently you exercise, the more immune system enhancement you can get. For example, one study has shown that people who walk at a very brisk pace for 40 minutes a day report half as many sick days as those who don't exercise.

Can Exercise Make You Get Sick?

But you can certainly overdo it. For example, nearly every time I finish an Ironman triathlon, I get sick 5-7 days later – and research has shown that as few as 90 minutes of high-intensity endurance exercise can make you more susceptible to illness for up to 3 days after the session.

The reason for this is a release of certain hormones that can cause a temporary decrease in the proper function of the immune system. When you perform a hard exercise session, you significantly increase the release of cortisol and adrenaline, which are your body’s “fight and flight” stress hormones. This can raise blood pressure and cholesterol levels, and simultaneously suppress the immune system.

As you probably guessed, if you are already sick with a cold or respiratory infection, high intensity exercise such as heavy weight lifting or very long exercise such as marathon training can further weaken the immune system.